Satellites, Remote Sensors Shed Light on Subterranean Structures

Photonics.comJun 2011
Jun. 17, 2011 — We all know that the lost city of Tanis is “one of the possible resting places of the Lost Ark” … those of us, anyway, who grew up thrilling to the exploits of the swashbuckling academic Indiana Jones. But now archaeologists may have made another important find in this ancient Egyptian city: pyramids.

Using infrared images taken by NASA satellites, Sarah Parcak and her team from the University of Alabama at Birmingham identified a number of structures buried deep beneath Tanis, including tombstones and houses as well as the suspected pyramids.

Remote sensing is an increasingly important tool in archaeology, and includes both aerial and satellite sensing (see hereto read about an aerial survey of the ancient Caracol using an advanced Lidar system to penetrate the dense jungle cover of present-day Belize). With satellite sensing, researchers look at the light reflected off the Earth in different parts of the spectrum to find traces of structures and past human activities. Based on differences in temperature they can identify irrigation ditches filled with sediment, for example, or buried stone walls.

Piecing it all together can provide a broad overview of a site, of roads, agricultural centers, entire cities. “You just pull back for hundreds of miles using the satellite imagery, and all of a sudden this invisible world become visible,” Parcak recently told NPR. “You're actually able to see settlements and tombs – and even things like buried pyramids – that you might not otherwise be able to see."

Seventeen of the structures in Parcak’s teams images had a size, shape and orientation similar to other pyramids in the area. Initial excavations have shown that at least two of these are most likely pyramids, though the researchers won’t be able to say with certainty until the sites have been excavated.

Robot sheds light on pyramid’s ancient markings

From satellites orbiting the earth to camera-equipped robots crawling through eight-inch-square shafts, modern technology has provided quite a boost to archaeology.

Recently, a robot explorer called Djedi has helped to shed light on mysteries of the Great Pyramid of Giza (the robot was named for the magician whom the pharaoh Cheops, or Khufu, consulted when planning the layout the pyramid). Creeping through tiny shafts, Djedi has transmitted back images of hieroglyphs not seen by human eyes in 4,500 years.

Discovered in 1872, the eight-inch-square shafts remained unexplored until 1993, when a German researcher sent a robot to investigate. This and subsequent attempts found limestone slabs adorned with two copper pins but, because the cameras on the robots could only see straight ahead, did not reveal as much as they might have.

Designed by University of Leeds engineer Rob Richardson, Djedi was equipped with a “micro snake” camera that could see around corners, and indeed was small enough to squeeze through a small hole in slab, offering investigators a view of the chamber beyond. This is where it found the hieroglyphs.

Now it’s up to archaeologists to decipher what they mean, and possibly determine the purpose of the shafts.

An acronym of light detection and ranging, describing systems that use a light beam in place of conventional microwave beams for atmospheric monitoring, tracking and detection functions. Ladar, an acronym of laser detection and ranging, uses laser light for detection of speed, altitude, direction and range; it is often called laser radar.